1-IN-1,000 YEARS ATLANTIC ROILING

Recent Hurricanes Not Matched Since Middle Ages
Jon Hamilton, August 12, 2009 (National Public Radio)

"The Atlantic Ocean is experiencing the most intense period of hurricane activity in 1,000 years, according to a [new] study…[that] looked at hurricane activity during the past 1,500 years using techniques that have emerged from a field often called paleotempestology.

"The discipline relies on scientists who hunt for physical evidence of ancient storms…by studying lagoons that are separated from the open ocean except when a hurricane causes water to rush over the land barrier…"

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"Studying [lagoon] layers is a bit like using tree rings to see what the weather was like hundreds of years ago…Paleotempestologists also search for evidence of conditions that would have favored hurricanes centuries ago. These include warm ocean temperatures in parts of the Atlantic and the presence of La Nina, an atmospheric phenomenon that creates wind conditions that help storms gain strength…Coral growth patterns can reveal when the water was warm. Ice cores help identify La Nina years…[Researchers] found that the conditions were ideal for hurricanes in the Middle Ages…"

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"Perfect conditions don't necessarily produce storms, though…[M]edieval sediments taken from lagoons between Massachusetts and Puerto Rico…confirmed that a number of storms actually had struck the coast during that period…It was probably a lot like the 2005 season, which was the busiest hurricane season in the Atlantic in recorded history. The season witnessed 28 named storms, including Katrina and Rita.

"But the current period of intense hurricane activity differs from the medieval one in an important way…Today's storms are associated primarily with warmer ocean temperatures, rather than the influence of La Nina…There is still debate among scientists about the effect of warmer water on hurricanes. And skeptics say it could have been a coincidence that the medieval storms came during a period of warm water and La Nina conditions…But the new research on ancient hurricanes is providing a kind of information that modern satellites and aircraft surveillance just can't…And this study…supports the idea that global warming is one reason we're seeing so many hurricanes these days."